Sean Yates abruptly quit cycling after 30 years of involvement both as rider and latterly as a team director when Team Sky announced on Sunday he was retiring. The 52-year-old Englishman -- who as a rider won stages on the Tour de France and the Tour of Spain -- leaves after a three year sojourn and which saw the team enjoy a stunning season with the highlight Bradley Wiggins winning the Tour de France. Yates had been one of the rare members of the cycling fraternity to defend disgraced American Lance Armstrong after he had all seven of his Tour de France titles stripped from him last Monday by the International Cycling Union over systematic doping. Yates had ridden alongside Armstrong at the Motorola team in the 1990\'s prior to the Texan being struck down with testicular cancer but also a spell when two of his team-mates testified that Armstrong decided to take banned products. Yates said in the time he worked with Armstrong at the Discovery Team -- the Englishman was sporting director at a time when the USADA report stated that systematic drug-taking was going on inside the outfit -- which included his last win in the Tour de France in 2005 he never saw him do anything illegal. \"It\'s all pretty damning for Lance and the whole history of his seven Tour wins, and beyond,\" he told BBC Radio earlier this month. \"My opinion is one of disappointment, I\'m upset, really. (I\'m shocked) at the depth of the whole system. I worked with Lance but never had any indication this practice was going on...it is disappointing,\" he said. \"I was there in 2005, for his last Tour win, and before then I was working with another team. \"I\'d turn up, I\'d drive the car in the Tour de France, and I never saw an indication of anything dodgy going on. I used to go out in the morning, go out on my bike, go back, drive the car, and call the tactics now and then, but I never saw anything untoward.\" Team Sky, though, were at pains to say that Yates\'s sudden departure had nothing to do with their position on anti-doping, wherein the management team started a series of individual interviews with riders, management and support staff. \"Sean has been interviewed and there were no admissions or disclosures that would have required him to leave the team,\" read the statement of the team. Team Sky supremo Dave Brailsford showered Yates with praise. \"Sean joined us in our first year and has been with us for three tough but rewarding seasons. \"After a long career in professional cycling, he has told us that he wants to move on, for purely personal reasons. \"Sean has been a great support to the riders on the road and a valuable colleague to us all. We wish him the best for the next step in his life.\"